Cause of death ideas?

[YSR50]

Lost a dark eyed LFABN today. Bought 3 of these 7 months ago. The other 2 as well as all other tank mates look and are acting fine.

Thanks for any help you can offer.

1. Water parameters
a) Temperature range. 79
b) pH. 6.8
c) GH. 100
d) KH 60
e)Ammonia, Nitrate, Nitrite, levels. 0, 20, 0
f) Water change frequency about 40-50% a week (2 x 20-25%)
(Most LFS's will check your water and give a list of readings).

2. Tank set up
a) Size. 20 gallon long
b) Substrate. none/bare
c) Filtration. SwissTropical Mattenfilter, Emperor 400
d) Furnishings. wood, plants, caves
e) Other tank mates. 6 x L201 breeding group plus a few loose fry/juvies, 2 other dark eyed LFABN, Orange shrimp, pest/assassin snails, 1 L270, 1 Peckoltia brevis
f) How long has it been set-up? About a year in it's current state
g) When was the last new fish added?about 2 weeks ago, 1 L270, 1 Peckoltia brevis
h) Foods used and frequency? Kens flake, worm sticks, catfish bits. Various Repashy foods. Frozen brine shrimp and blood worms. 1 - 2 small feedings a day

3. Symptoms / Problem description Dark abdomen, see pictures

4. Action taken (if any) none

5. Medications used (if any) none, looking for advice

[Jools]

The dark abdomen is just it's been eating something that colour perhaps algae? I can't see any obvious sign indicating a problem.

Jools

[YSR50]

The dark abdomen is just it's been eating something that colour perhaps algae? I can't see any obvious sign indicating a problem.

Jools

Perhaps, although I would think the other 2 LFABN would also show some color. Obviously I would not be able to notice any darkening on the others. Forgot to mention that I noticed the dark color a few days ago, but it was just a small section on one side.

Not that I don't care about the BNs or L201s, but I'm more worried about cross contaminating my other tanks since I use the same Python when doing water changes.

[TwoTankAmin]

Just so you are aware, not all fish die from the well known diseases, parasites worms etc. Just like all other animals, they can be born with genetic and or physiological defects. They can have a heart attack or a stroke. There are plenty of things that may be wrong that can cause premature death.

Since there are no apparent markings on the dead fish that would indicate it was assaulted, I think that can be ruled out. Since you have no obvious evidence for a cause of death, consider the possibility it may have been due to "natural" causes. Over the last 16 years I have lost 3 large and/or long term held clown loaches. Only the most recent one showed any symptoms. Mostly it never came out even when I fed. Before I could find and catch it, it died. I actually froze and sent the first one that died about 12 years ago to somebody to do a physiological autopsy. He found nothing looking out of the ordinary, Gills fine, no blockages or twisted intestines, no tumors etc. He was the first person to make me aware that fish do die of natural causes.

On the other hand it may have died from a disease or infestation which did not manifest any external symptoms. But knowing this would require some form of an autopsy, likely in a lab setting.

While nobody likes having their fish die, what makes it even worse is not knowing why because we do not know if it will affect other tank inhabitants. The best course of action here, imo, is to monitor the tank closely for the next few weeks. Watch for unusual behavior as well as any symptoms.

[YSR50]

Thanks.
The fact that the abdomen turned dark before it died made me wonder if there might be something I should treat the tanks with as a preventative measure. But like you said, probably will never know.

Been keeping/breeding fish for over 30 years so I'm fully aware of the "old age/natural causes" possibility. Most of my tanks are established breeding setups and I rarely purchase random fish through pet stores. When I do, I use a QT but once in a while I'm lazy, and of course I (my fish) usually pay for it in the end.